Intervertebral implants, instruments, and methods

ABSTRACT

In accordance with one aspect, a spinal implant for fusing vertebral bones is provided that includes a monolithic body for being inserted between bones. The body has a through opening of the body for receiving bone growth material and a wall of the body extending about the through opening. The wall includes nubs extending into the through opening that increase the surface area of the wall available for bone on-growth.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent App. No.62/555,966, filed Sep. 8, 2017, which is hereby incorporated byreference herein in its entirety.

FIELD

This disclosure relates generally to implantable medical devices and,more specifically, to implantable devices for intervertebral fusionand/or immobilization.

BACKGROUND

Many people develop back pain during their lifetimes due to injury,disease, or genetic defect. One source for back pain is if anintervertebral disc of a patient bulges outward from between theassociated vertebrae. The bulging disc may impinge on the nerves of thespine and cause pain. To address this situation, a surgeon may trim thedisc bulge or remove the disc entirely. The surgeon may then insert oneor more implants to support and separate the vertebrae.

One type of implant used to support and separate vertebrae are interbodyfusion devices (“IBDs”). IBDs often have a body with a large throughborein which bone growth material can be packed to encourage bony ingrowthfrom the vertebrae and into the throughbore. One type of IBD is made ofpolyetheretherketone (PEEK). Although PEEK implants are radiolucent anddo not obstruct x-ray viewing of the surgical site post-surgery, PEEKimplants have been found to exhibit minimal amounts of bone growth ontothe PEEK implant. PEEK IBDs may have a series of ridges in thethroughbore that each extend continuously around the throughbore. Thesecontinuous ridges retain the bone growth material in the throughbore.The ridges extended continuously around the throughbore to maximizepurchase with the bone growth material.

Another type of IBD is made of titanium-coated PEEK. The titaniumcoating has a roughened outer surface and encourages bone growth ontothe implant. However, the titanium coating is radio-opaque and obstructsx-ray viewing of the surgical site post-surgery.

SUMMARY

In accordance with one aspect of the present disclosure, a spinalimplant is provided for fusing vertebral bones. The spinal implantincludes a monolithic body for being inserted between bones, a throughopening of the body for receiving bone growth material, and a wall ofthe body extending about the through opening. The spinal implant furtherincludes nubs of the wall extending into the through opening thatincrease the surface area of the wall available for bone on-growth. Theincreased surface area provides more area for bone to bond with theimplant which increases the strength of the implant-vertebrae construct.The nubs of the wall also help retain the bone growth material withinthe through opening of the body which makes the implant easier toadvance into the intervertebral space.

In one form, the monolithic body includes polyetherketoneketone (PEKK)and is fabricated using selective laser sintering. Fabricating the bodyby selective laser sintering PEKK produces rough surfaces of the bodyincluding surfaces of the nubs. For example, the rough surfaces of thebody may have nanostructures that resemble peaks and valleys between thepeaks, with an average peak-to-valley distance of approximately 125-129nanometers and an average peak-to-peak distance of approximately 265-282nanometers. It has been discovered that the combination of the increasedsurface area of the nubs and the roughness of the surfaces of the nubsencourages significant bone fusion interaction within the throughopening of the body. Further, because the body is made from PEKK, thebody is radiolucent to x-rays and permits a surgeon to view the surgicalsite post-surgery without obstruction by the implant body. This is animprovement over prior titanium-coated PEEK implants that areradio-opaque and obstruct viewing of the surgical site with x-rays. Inthis manner, the PEKK implant body provides both significant boneon-growth and a radiolucent implant for improving x-ray observation ofthe implant post-surgery.

In another aspect, an implant is provided for being inserted into anintervertebral space to stabilize vertebrae. The implant includes amonolithic body having a through opening for receiving bone growthmaterial and an annular wall extending about the through opening. Theannular wall is free of through apertures in communication with thethrough opening. In one embodiment, the monolithic body is made of PEKKand is fabricated using selective laser sintering. Although PEKK has arelatively high strength, PEKK becomes more brittle at narrowthicknesses. The absence of through apertures strengthens the annularwall of the body so that the annular wall can resist loading from thevertebrae after implantation, even at thin wall thickness such as 0.06inches.

The body also includes an attachment member outward of the annular walland recesses extending along opposite sides of the attachment member.The recesses are configured to receive clamping arms of an insertertool. Because the inserter tool engages the implant by engaging theclamping arms with the attachment member, loading applied to theinserter tool such as by the surgeon moving the inserter tool in lateraldirections is applied to the implant along opposite sides of theattachment member. Using opposite sides of the attachment member toreceive loading from the inserter tool more evenly distributes loadingfrom the inserter tool to the implant and minimizes stressconcentrations on the implant due to the engagement with the clampingarms.

A spinal implant is also provided that includes a polymer bodyfabricated using additive manufacturing. The body has unmachined,irregular surfaces due to the body being fabricated by additivemanufacturing. The irregular surfaces actively participate in boneon-growth which improves the strength of the engagement between theimplant and bones. The body also includes a machined attachment portionfor interfacing with an inserter tool. By machining the body, tighttolerances can be achieved for the attachment portion. The attachmentportion has a surface roughness that is less rough than a surfaceroughness of the unmachined, irregular surfaces of the body. In thismanner, the implant has both unmachined, irregular surfaces to encouragebone on-growth and a machined attachment portion with a reduced surfaceroughness that provides the high accuracy machined structures necessaryto properly engage the inserter tool. In one embodiment, the plasticbody is made of PEKK and is fabricated using selective laser sintering.

In accordance with another aspect of the present disclosure, a spinalimplant system is provided that includes a spinal implant and aninserter tool. The spinal implant has a leading end portion, a trailingend portion, and a longitudinal axis extending therebetween. The tailingend portion includes an attachment member, and the attachment member hasa boss extending axially outward from a trailing end surface of theattachment member. The inserter tool includes arms having a releaseconfiguration that permits the arms to be positioned on opposite sidesof the attachment member and a gripping configuration wherein the armsclamp the attachment member therebetween. The inserter tool alsoincludes a socket configured to engage the boss of the attachment memberand increase the axial length of the engagement between the insertertool and the implant. By increasing this axial length, the forcesapplied by the surgeon to the inserter tool as the surgeon manipulatesthe inserter tool (e.g., in the cephalad/caudal directions) is appliedto the implant over a longer axial extent which more evenly distributesthe forces and strengthens the connection between the implant and theinserter tool.

The present disclosure also provides a method of producing a spinalimplant. The method includes fabricating a body of the spinal implantmade of a polymer material using an additive manufacturing process. Thebody includes irregular outer surfaces having a first surface roughnessproduced by the additive manufacturing process. The method furtherincludes machining the fabricated body to form an attachment portion ofthe body for interfacing with an inserter tool. The attachment portionhas a second surface roughness that is less rough than the first surfaceroughness of the irregular outer surfaces of the body. The irregularouter surfaces of the fabricated body actively participate in boneon-growth which improves the strength of the engagement between theimplant and bones. Further, by machining the fabricated body, tighttolerances can be achieved for the attachment portion. The methodthereby provides a spinal implant having rougher irregular outersurfaces to encourage bone on-growth and a smoother attachment portionfor precise engagement with an inserter tool.

In accordance with another aspect, a marker pin is provided for a spinalimplant. The marker pin includes a body of a radiopaque material and aleading end portion of the body sized to fit into an opening of a bodyof a spinal implant. The body further includes an interference portionradially enlarged relative to the leading end portion and configured toengage the spinal implant body at a plurality of circumferentiallyspaced locations about the opening and retain the marker pin in theopening of the spinal implant body. Because the interference portionengages the spinal implant body at circumferentially spaced locations,there are undeformed portions of the spinal implant body separatinglocalized deformations caused by the interference portion. This permitsthe marker pin to deform less of the material of the spinal implant bodyaround the opening and makes the implant stronger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an implant showing rough, irregularsurfaces of the implant formed by fabricating the implant by selectivelaser sintering PEKK and smoother surfaces of the implant formed bymachining portions of the body;

FIG. 2 is a side elevational view of the implant of FIG. 1 showing apattern of nubs and pathways on a side of the implant;

FIG. 3 is a top plan view of the implant of FIG. 2 showing an annularwall of the implant extending around a through opening of the implantfor receiving bone growth material;

FIG. 4 is a cross-sectional view taken across line 4-4 in FIG. 3 showinga pattern of nubs and pathways on an inner surface of a wall of theimplant;

FIG. 5 is a cross-sectional view taken across line 5-5 in FIG. 2 showingan attachment member for being clamped between arms of an inserter tool;

FIG. 6 is a rear elevational view of the implant of FIG. 2 showingrecesses on opposite sides of the attachment member that receive theinserter tool arms;

FIG. 7 is a perspective view of a marker pin of the implant of FIG. 2showing flats and edges of the marker pin;

FIG. 8 is a top plan view of the marker of FIG. 7 in an opening of theimplant of FIG. 2 and the edges of the marker pin engaging a body of theimplant at spaced locations around the opening;

FIG. 9 is a perspective view of another implant showing rough, irregularsurfaces of the implant formed by fabricating the implant by selectivelaser sintering PEKK and smoother, machined surfaces of the implant;

FIG. 10 is a cross-sectional view of the implant taken across line 10-10in FIG. 9 showing a pattern of pathways and nubs on an inner surface ofthe implant;

FIG. 11 is a cross-sectional view taken across line 11-11 in FIG. 10showing a web of the implant extending across a through opening of theimplant;

FIG. 12 is a rear elevational view of the implant of FIG. 9 showingrecesses on opposite sides of an attachment member of the implant forreceiving arms of an inserter tool;

FIG. 13 is a perspective view of an implant showing rough, irregularsurfaces of the implant formed by fabricating the implant by selectivelaser sintering PEKK and smoother, machined surfaces of the implant;

FIG. 14 is a top plan view of the implant of FIG. 13 showing a throughopening of the implant and an annular wall extending around the throughopening;

FIG. 15 is a side elevational view of the implant of FIG. 14 showing awedge-like profile of the implant;

FIG. 16 is a cross-sectional view taken across line 16-16 in FIG. 14showing a pattern of nubs and pathways of an inner surface of theannular wall;

FIG. 17 is a cross-sectional view taken across line 17-17 in FIG. 15showing an attachment member of the implant for being clamped by arms ofan inserter tool;

FIG. 18 is a rear elevational view of the implant of FIG. 13 showingrecesses on opposite sides of the attachment member for receiving theinserter tool arms;

FIG. 19 shows an engineering model of an implant body and the implantbody that results from selective laser sintering PEKK based on themodel;

FIGS. 20, 21, and 22 are perspective views of bodies of implantsfabricated by selective laser sintering PEKK and the bodies after thebodies have been machined;

FIGS. 23, 24, and 25 are views showing the orientation of the implantbodies of FIGS. 20, 21, 22 during the selective laser sinteringprocedure;

FIG. 26 is an image of different types of pins implanted during asurgical trial including a pin that was formed by selective lasersintering PEKK and includes nubs;

FIG. 27 is an image of the pin implants of FIG. 26 after being removedfrom the test subjects;

FIG. 28A, 28B, 28C, 29A, 29B, 29C are cross-sectional pictures of pinssimilar to the pins of FIG. 26 in bone showing the most pronounced boneattachment to the pin implant formed by selective laser sintering PEKK;

FIG. 30 is a graph showing the push-out resistance of differentmaterials;

FIG. 31 is a perspective view of an inserter tool for inserting theimplant of FIG. 1;

FIG. 32 is a cross-sectional view of a proximal portion the insertertool of FIG. 31 showing a plunger-shaped adjustment knob that controlsconnecting of the implant to the inserter tool and a rotatable lock knobfor securing the adjustment knob in a locked position;

FIG. 33 is a cross-sectional view of a distal portion of the insertertool of FIG. 31 showing a clamping arm of the inserter tool in an openposition;

FIG. 34 is a view similar to FIG. 33 showing the clamping arm pivoted toa closed position to clamp an attachment member of the implant betweenthe clamping arm and a fixed arm of the inserter;

FIG. 35 is a cross-sectional view taken across line 35-35 in FIG. 34showing the boss of the implant received as a plug in a socket of adistal end of the inserter tool;

FIG. 36 is a top plan view of the inserter tool of FIG. 31 and theimplant of FIG. 2 showing the adjustment knob in a release position andthe lock knob in an unlocked position;

FIG. 37 is a top plan view similar to FIG. 36 showing the adjustmentknob in a gripping position and the lock knob in an unlocked position;

FIG. 38 is a view similar to FIG. 37 showing the lock knob turned to alocked position;

FIG. 39 is an elevational view of an inserter tool for inserting theimplant of FIG. 9;

FIG. 40 is a cross-sectional view of the inserter tool of FIG. 39showing a handle assembly and a shaft assembly of the inserter tool;

FIG. 41 is a cross-sectional view of a distal end of the shaft assemblyof FIG. 40 connected to the implant of FIG. 9;

FIG. 42 is a cross-sectional view taken across line 42-42 in FIG. 41showing a boss of the implant received as a plug in a socket of arms ofthe shaft assembly of FIG. 40;

FIG. 43 is a perspective view of an inserter tool for inserting theimplant of FIG. 13;

FIG. 44 is a cross-sectional view of a distal end of the inserter of theFIG. 43 and the implant of FIG. 13 showing arms of the inserter in arelease position ready to receive the attachment member of the implant;and

FIG. 45 is a cross-sectional view similar to FIG. 44 showing the arms ofthe inserter in clamping positions to secure the arms to the implant.

DETAILED DESCRIPTION

With reference to FIG. 1, an implant 10 is provided for stabilizingvertebrae. The implant 10 has a body 15 that may be made of a plastic,such as polyetherketoneketone (PEKK), and may be fabricated using a 3Dprinting or additive manufacturing process, such as selective lasersintering. The fabrication of the implant 10 by selective lasersintering PEKK creates rough surfaces 12 of the body 15 due to thegranule powder size and resolution of the selective laser sinteringprocess. The rough surface texture of the rough surfaces 12 is indicatedby stippling in the drawings. The rough surfaces 12 have nanostructuresthat resemble peaks and valleys between the peaks, with an averagepeak-to-valley distance of approximately 125-129 nanometers and anaverage peak-to-peak distance of approximately 265-282 nanometers. Theseparameters were measured using an XE7 atomic force microscope having anon-contact cantilever probe (from Park Systems of South Korea) with aforce constant of 42 N/m, a scan size of 1×1 micrometer, and a scanfrequency of 0.5 Hz.

The rough surface also includes micro-size pores having an average porediameter in the range of approximately 500 micrometers to approximately600 micrometers, such as approximately 530 micrometers. Further, theimplant 10 has nubs 14 and 16 that are macro-size structures whichincrease the surface area of the surfaces 12 of the implant 10.

The combination of the rough exterior surfaces 12 and the nubs 14, 16results in deeper implant osseointegration than if the implant were madeof PEEK or titanium plasma coated PEEK, as discussed in greater detailbelow. In other words, the rough exterior surfaces 12 and nubs 14, 16allow more bone cells to attach to more of the implant 10.

The implant body 15 has a leading end portion 18 and a trailing endportion 20. The leading end portion 18 includes a tapered nose 22 andthe trailing end portion 20 includes an attachment portion 23 includingan attachment member 24 and recesses 26, 28. The body 15 may be machinedafter being fabricated to create the features of the nose 22, attachmentmember 24, and recesses 26, 28 in the body 15. The term machined isintended to mean that the implant is secured and a moving cutting memberis brought into contact with the implant to remove material from thebody of the implant. Machining can include, but is not limited to, CNCmachining including mills and turning centers. Machining the body 15 toform the nose 22 forms smooth surfaces 30 of the nose 22 and machiningthe body 15 to form the attachment member 24 and recesses 26, 28 createssmooth surfaces 32. The smooth surfaces 30 of the nose 22 make it easierto advance the implant 10 into an intervertebral space. The smoothsurfaces 30, 32 have a surface roughness approximately 30-60 roughnessaverage or 30-65 root mean squared, compared to the unmachined surfaces12 having a surface roughness in the range of 900 to 1100 roughnessaverage, such as approximately 1000 roughness average (approximately1100 root mean squared). The machining thereby smooths out theirregularities that create the rough surfaces 12 produced by selectivelaser sintering PEKK.

Machining the attachment member 24 and recesses 26, 28 into the body 15provides high accuracy for the geometry of the attachment member 24 andrecesses 26, 28 that may not be possible by selective laser sinteringPEKK. High accuracy of the attachment member 24 and recesses 26, 28provides desired tolerances so that the attachment member 24 may beproperly secured to an inserter tool. In this manner, the implant 10combines the rough surfaces 12 from fabricating of the body 15 thatimprove bone on-growth to the implant 10, the high-accuracy geometry ofthe attachment member 24 and recesses 26, 28 which allow the implant 10to be securely grasped by an inserter tool, and the smooth profile ofthe nose 22 to improve insertion of the implant 10.

With reference to FIGS. 1 and 2, the body 15 includes an annular wall 34encircling a compartment, such as formed by a through opening 35, forreceiving bone growth material. The bone growth material may includeautograph, allograph, allogenic bone graft, demineralized bone matrix,hydroxyapatite. The annular wall 34 includes lateral wall portions 36,38 spaced apart from each other on opposite sides of the through opening35. The lateral wall portions 36, 38 have an outer surface 40 with apattern 42. The pattern 42 includes the nubs 14 and pathways 44 betweenthe nubs 14. The nubs 14 increase the surface area of the outer surface40 for bone to grow onto. The pathways 44 provide spaces for bone togrow along the outer surfaces 40 of the lateral walls portions 36, 38.

The lateral wall portions 36, 38 each have an inner surface 50 with apattern 52 that includes the nubs 16 and pathways 54 as shown in FIG. 1.The nubs 16 increase the surface area of the inner surface 50 foron-growth of bone and assist in the retention of the bone growthmaterial within the though opening 35 during installation of the implant10 between adjacent vertebrae. The pathways 54 provide spaces betweenthe nubs 16 through which bone growth material is packed and retained asthe surgeon packs the through opening 35 with bone growth material.

Further, after the body 15 has been fabricated by selective lasersintering PEKK, the body 14 can be low pressure blasted to remove excessPEKK leftover from the selective laser sintering process. The leftoverPEKK on the body 15 resembles hardened clumps of sand that is broken offfrom the body 15. The low pressure blasting may involve pressures lessthan 20-100 pounds per square inch, such as 50 pounds per square inch,and may utilize glass, bead, sand, and/or dry ice particles as theblasting medium. The pathways 54 permit particles from the low pressureblast process process to travel along the inner surface 50 and removeleftover PEKK from the inner surface 50. For example, with reference toFIG. 4, the low pressure blasting particles can travel in direction 104through the pathway 54A. This allows the low pressure blasting particlesto remove debris from difficult-to-reach portions of the inner surface50, such as the undersides of the nubs 16. In this manner, the pathways54 make it easier to clean the body 15 after fabricating the body 15.

With reference to FIG. 2, the annular wall 34 includes an upper boneengaging portion 55 and a lower bone engaging portion 56. The upper andlower bone engaging portions 55, 56 may be oriented to have angles 58,60 of zero to eighteen degrees so that the upper and lower bone engagingportions 55, 56 match the patient's anatomy. The upper and lower boneengaging portions 55, 56 may thereby taper toward each other as the body15 extends from the nose 22 to the attachment member 24. The upper andlower bone engaging portions 55, 56 include gripping members 62separated by recesses 64. The gripping members 62 each have a peak 66 atwhich a trailing surface 68 and a leading surface 70 meet. The peak 66may be sharp to engage the end plates of the vertebrae. The grippingmembers 62 may have various shapes, such as saw teeth, sine wave,pyramids, curved teeth, etc.

The pattern 42 extends from the upper bone engaging portion 55 to thelower bone engaging portion 56 along the outer surfaces 40 of each ofthe lateral wall portions 36, 38. The pathways 44 form a lattice pattern72 as shown in FIG. 2. The lattice pattern 72 includes crisscrossingpathways 44 such as pathway 44A and pathway 44B that each extend fromthe upper bone engaging portion 55 to the lower bone engaging portion56. The pathways 44A, 44B may have a variety of shapes including linearand non-linear. For example, the pathway 44A may have a first pathwayportion 74 and a second pathway portion 76 that extend transversely toeach other. One or more of the pathways 44 may be curved or have aportion that is curved.

The crisscrossing pathways 44 can define the general shape of the nubs14. In one form, the nubs 14 have a diamond-like shape. With respect tonub 14A, the nub 14A has a continuous peripheral outer surface extendingthereabout including sides 80, 82, 84, 86. The pairs of sides 80, 82 and84, 86 are each oriented at angles 88 relative to each other. The shapeof the nubs 14 may change throughout the pattern 42. For example, thenub 14B has sides 80, 82, 84, 86 and each pair of sides 80, 82, and 84,86 are oriented at angles 98 that are smaller than the angles 88. Thenub 14A therefore appears elongated while the nub 14B more resembles asquare. With reference to FIGS. 1 and 2, the sides 80, 82, 84, 86 of thenubs 14 extend outward from base surfaces 96 of the pathways 44generally perpendicular to the base surfaces 96.

With reference to FIG. 4, the pattern 52 on the inner surface 50 of eachof the lateral wall portions 36, 38 includes the nubs 16 and pathways54. The pathways 54 include openings 100 at the upper bone engagingportion 55 and openings 102 at the lower bone engaging portion 56. Thepattern 52 includes recessed base surfaces 107 separating the nubs 16.Due to the openings 100, 102, the recessed base surfaces 107 extend allthe way between the top and bottom of the body 15. The base surfaces 107and nubs 16 define the pathways 54. For example, the pathway 54A extendsfrom the opening 100A to the opening 102A. The pathway 54A permits bonegrowth material to move in the through opening 35 in direction 104between the nubs 16. The pathways 54 intersect each other and form alattice 103 of crisscrossing or intersecting pathways 54. For example,the pathway 54B extends from the upper bone engaging portion 55 to thelower bone engaging portion 56 and intersects the pathway 54A. Theintersecting pathways 54 define the general shape of the nubs 16. Thenubs 16 each have a continuous peripheral surface 106 that extends fromthe base surface 107 of the pathways 54. The peripheral surface 106 ofeach nub 16 is completely spaced from the peripheral surface 106 of thesurrounding nubs 16. The nubs 16 are localized protrusions that extendinto the through opening 35 from the base surfaces 107 of the pathways54.

With reference to nub 16A, the peripheral surface 106 of the nub 16Aincludes side surfaces 108A, 108B, 108C, 108D that are interconnected bycorner edges 110. The side surfaces 108B, 108D are oriented to extend toan angle 112 relative to one another, and the side surfaces 108A, 108Care oriented to extend at an angle similar to angle 112. The sidesurfaces 108B, 108C are oriented to extend at an angle 114 relative toone another and the side surfaces 108A, 108D are oriented to extend atan angle similar to angle 114. The angle 114 is larger than the angle112 such that the nub 16A is elongated along a vertical axis 109 of thebody 15. The angle 112 may be approximately 60 degrees and the angle 114may be approximately 120 degrees. The side surfaces 108A-108D may eachextend obliquely into the through opening 35 relative to the basesurfaces 107 of the pathways 54. This provides a more tapered profile ofthe nubs 16 as the nubs 16 extend at an incline into the throughbore 35than the nubs 14. The obliquely inclined side surfaces 108A-108D mayfunction as ramps to direct debris off of the nubs 16 during lowpressure blasting of the body 15 after the body 15 has been fabricatedusing selective laser sintering. This makes the body 15 easier to cleanafter fabrication.

With reference to FIGS. 5 and 6, the trailing end portion 20 includesthe attachment member 24 and recesses 26, 28 on opposite sides of theattachment member 24. The recesses 26, 28 receive arms of an insertertool. The attachment member 24 has a neck portion 130 and a head portion132. The neck portion 130 is recessed from lateral sides 134, 136 of thelateral wall portions 36, 38. The head portion 132 and neck portion 130permit the inserter tool arms to be received so that their outersurfaces are laterally inward from or flush with the lateral sides 134,136. Because the inserter tool arms are inward from or flush with thelateral sides 134, 136, the inserter tool arms avoid becoming caught ontissue or bone as the implant 10 is advanced into the intervertebralspace.

The neck portion 130 can have a width 138 of approximately 0.170 inchesand the head portion 132 can have a width 139 of approximately 0.240inches such that the head portion 132 is enlarged relative to the neckportion 130. The width 138 may be in the range of approximately 0.118inches to approximately 0.197 inches and the width 139 may be in therange of approximately 0.197 inches to approximately 0.276 inches. Theratio of the width 139 to the width 138 may be in the range of 1.1 to2.4, such as 1.3 to 2.0, and may be approximately 1.4. The head portion132 and neck portion 130 provide a thick, block-like structure for theinserter tool arms to engage and grab. The overall width of the implant10 between the sides 134, 136 may be approximately 0.394 inches.

The attachment member 24 also includes a boss 140 extendinglongitudinally for a distance 142 from a trailing end surface 144 of theattachment member 24. The trailing end surface 144 may be flat, and theboss 140 may have a generally cuboid shape that extends rearward fromthe trailing end surface 144. The boss 140 operates as a plug that fitswithin a socket of the inserter tool (see FIG. 35) to increase thelength of the engagement between the implant 10 and the inserter tool.This improves the strength of the connection between the implant 10 andthe inserter tool by providing better torque resistance as discussed ingreater detail below.

With reference to FIG. 6, the implant body 15 includes ceilings 850,floors 852, and lateral sides 851, 853 of the attachment member 24defining the recesses 26, 28. The body 15 includes corners 855, 857connecting the ceilings 850 and floors 825 to the lateral sides 851,853. The corners 855, 857 are relatively sharp, such as 90 degrees. Bymachining the PEKK material, the corners 855, 857 of the implantattachment portion 23 can be formed with tight tolerances. Further, thesomewhat U-shaped recesses 26, 28 extending laterally inward into thebody 15 as shown in FIG. 6 provide pockets to receive the arms of aninserter tool with the outer surfaces of the arms laterally inward fromor flush with the lateral sides of the implant 10.

With reference to FIGS. 4 and 5, the body 15 includes through apertures120, 122 for receiving marker pins 124. The marker pins 124 may beradiolucent to indicate the orientation of the implant 10 during x-rayimaging of the surgical site. Turning to FIG. 7, each marker pin 124 mayhave a trailing end portion such as an upper end portion 150, a leadingend portion such as a lower end portion 152, and an interference portionsuch as an enlarged portion 154 intermediate the upper and lower endportions 150, 152. The enlarged portion 154 has a larger radius than theapertures 120, 122 to be in interference therewith.

The upper and lower portions 150, 152 have a circular cross-section andthe enlarged portion 154 has a non-circular cross-section, such as apolygonal cross-section such as the illustrated generally rectangularcross section. As illustrated, the enlarged portion 154 includes flats156 and corner junctures or edges 158 which connect the flats 156. Whenthe marker pins 124 are received in the body apertures 120, 122, theedges 158 engage the surfaces about the apertures 120, 122 to deform thematerial of the body 15 and fix the marker pin 124 within the apertures120, 122. By deforming the material of the body 15 with the edges 158,the marker pin 124 deforms a smaller portion of the body around theapertures 120, 122 which reduces the likelihood of the body 15fracturing around the apertures 120, 122. Using the edges 158 to locallydeform the material of the body 15 provides reduced stress in the body15 in comparison to a cylindrical marker pin having a diameter largerthan the apertures 120, 122 that is press fit into the apertures 120,122 and engages the body 10 around the entire circumference of themarker pin.

For example and with reference to FIG. 8, the through bore 122 has anopening surface 160 extending around the opening 122. As the marker pin124 is advanced into the opening 122, the edges 158 bite into thesurface 160 and create localized deformations 162 of the body 15 at eachof the edges 158. Because the marker pin 154 has flats 156 separatingthe edges 158, the implant body 15 has undeformed portions 164separating the localized deformations 162. By deforming less of the areaof the opening surface 160, the implant 15 is stronger due to thereduced stress in the material of the body 15 surrounding the apertures120, 122.

As noted above, PEKK is more brittle than PEEK at smaller features suchas relatively thin wall portions 36, 38. To increase the strength of theannular wall 34, the annular wall 34 is free of through apertures incommunication with the through opening 35 that extend between the innerand outer surfaces 40, 50 and would otherwise cause stressconcentrations in the annular wall 34. The annular wall 34 is thereforestronger in compression which makes the implant 10 more durable. Throughapertures are often used in the walls of PEEK implants to permit bonegrowth through the aperture. Although the annular wall 34 lacks throughapertures that permit bone growth therethrough, the rough exteriorsurfaces 12 and the nubs 14, 16 provide significant implantosseointegration without through apertures.

With reference to FIG. 9, an implant 200 is provided that a similar inmany respects to the implant 10 discussed above such that differencesbetween the implants 10, 200 will be highlighted. The implant 200includes a body 202 having a leading end portion 204 and a trailing endportion 206. The body 202 may be formed by selective laser sinteringPEKK and has rough, unmachined surfaces 208. The trailing end portion206 includes an attachment portion 213 including an attachment member215 and recesses 214, 216 on opposite sides of the attachment member215. The nose 210 and attachment portion 213 are machined into the body202 after the body 202 has been fabricated such that the nose 210 andattachment portion 213 have smooth, machined surfaces 212, 217.

With reference to FIG. 9, the body 202 includes an annular wall 220extending around a compartment, such as a through opening 221. Thethrough opening 221 receives bone growth material. The annular wall 220includes lateral side walls 222, 224 and the body 202 includes a web 226extending between the lateral side walls 222, 224. The annular wall 222has an inner surface 230 defining at least a portion of the throughopening 221. The inner surface 230 includes nubs 232.

With reference to FIGS. 10 and 11, the implant 200 includes alongitudinal axis 240, a vertical axis 242, and a lateral axis 338. Theweb 226 extends across the through opening 221 transverse, such asperpendicular, to axes 240, 242 and along the lateral axis 338. The web226 has a base 244 that tapers outwardly as the web 226 reaches theinner surface 230 at each of the lateral side walls 222, 224. Theannular wall 220 includes an upper bone engaging portion 250 and a lowerbone engaging portion 260. The upper and lower bone engagement portions250, 252 include gripping members 254 that each have a peak 256, aleading surface 258, and a trailing surface 260. The upper and lowerbone engaging portions 250, 252 include recesses 262 between thegripping members 254. The peaks 256 may be rounded and the leading andtrailing surfaces 258, 260 may also be rounded to form an undulatingsurface of the upper and lower bone engaging portions 250, 252.

The web 226 has an uppermost portion 251 and a lowermost portion 253that include, respectively, a top surface 255 and a bottom surface 257.The uppermost and lowermost portions 251, 253 are recessed relative tothe upper and lower bone engaging portions 250, 252. Because theuppermost and lowermost portions 251, 253 of the web 226 are recessed,the web 226 avoids contacting bones during insertion of the implant 200into an intervertebral space between the bones. This reduces the surfacearea of the implant 200 that can contact the bones and resist advancingof the implant 200 into the intervertebral space. If the body 202 isfabricated by selective laser sintering PEKK, the body 202 may be morebrittle than an implant milled from a block of PEEK. The recessed web226 may reduce the resistance to advancing the implant 200 such that thesurgeon may apply less force to the implant 200 via an inserter tool.

The web 226 may have a rectangular cross-section taken normal to thelateral axis 338 and the web 226 has top and bottom surfaces 255, 257that may be flat or rounded. The top and bottom surfaces 255, 257 extendfrom one lateral side wall 222, 224 to the other. The top and bottomsurfaces 255, 257 of the web 226 may each be spaced from the peaks 256of the gripping members 254 of the respective upper and lower boneengaging portions 250, 252 by a distance 261. The implant 200 may beprovided in various heights 263 and the web 226 has a height 265 thatmay be the same for different heights 263 of the implant 200. Thus, thedistance 261 may be greater for taller implants 200 than for implants200 with shorter heights 263.

With reference to FIG. 10, the annular wall 220 includes a pattern 264and includes the nubs 232 and intersecting or crisscrossing pathways 268that form a lattice. The pathways 268 include openings 270 at the upperbone engaging portion 250 and openings 272 at the lower bone engagingportion 252. The pathways 268 permit low pressure blasting particles totravel therethrough and remove debris left on the nubs 232 fromfabrication of the body 202. The pathways 268 also permit bone growthmaterial to travel between the nubs 232 as the bone growth material ispacked into the through opening 221. The nubs 232 have a shape similarto the nubs 16 discussed above and extend inwardly from base surfaces280 of the pathways 268. The nubs 232 therefore increase the surfacearea of the inner surface 230 of the annular wall 220 to improve boneon-growth. The nubs 232 also operate to retain bone growth material inthe through opening 221.

With reference to FIGS. 10 and 11, the trailing end portion 206 includesa substantially flat trailing end surface 284 and the attachment member215 includes a rectangular boss 290 that extends longitudinally outwardfrom the trailing end surface 284 a distance 292. The boss 290 forms aplug-fit engagement with a socket of an inserter tool as discussed ingreater detail below with reference to FIG. 42. The boss 290 increasesthe longitudinal length of engagement between the inserter and theimplant 200 to distribute loading from the inserter to the implant 200over a larger portion of the implant 200 which limits stressconcentrations in the body 202. The leading and trailing end portions204, 206 also include bores 296 for receiving marker pins 298.

With reference to FIG. 11, the attachment member 215 includes secondaryrecesses, such as cavities 300, 302, for receiving projections of armsof an inserter tool. The attachment member 215 includes walls 304, 306,308 that define the cavities 300, 302. The wall 304 on each side of theattachment member 215 is oriented to extend transverse to thelongitudinal axis 240 such that the engagement between the inserter toolarms and the walls 304 cams the attachment member 215 toward theinserter tool as the arms clamp the attachment member 215 therebetween.In this manner, the more tightly the arms of the inserter clamp theattachment member 215, the more the implant 200 is urged proximally intothe inserter tool.

With reference to FIG. 12, the body 202 includes outer lateral surfaces320, 322 extending from the upper bone engaging portion 250 to the lowerbone engaging portion 252. In one form, the lateral surface 320 istaller than the lateral surface 322 such that one lateral side of theimplant 200 is taller than the other side. This allows the implant body202 to match the patient anatomy.

In some forms, the body 15 of the implant 10 is fabricated usingadditive manufacturing and materials other than PEKK. For example, thebody 15 may be made of various types of polymers and metallic materials.Further examples include ceramic, hydroxylapatite, titanium, and PEEK.

With reference to FIG. 13, an implant 400 is provided for beingpositioned between vertebrae, such as cervical vertebrae, and is similarin many respects to the implants 10, 200 discussed above. The implant400 has a body 402 that may be fabricated by selective laser sinteringPEKK, which results in rough outer surfaces 404 of the body 402. Thebody 402 includes a leading end portion 406 and a trailing end portion408. The trailing end portion 408 includes recesses 410, 412 and anattachment member such as a dovetail projection 414 intermediate therecesses 410, 412. The recesses 410, 412 and the dovetail projection 414are machined into the body 402. This causes the trailing end portion 408to have smooth machined surfaces 416.

The body 402 includes an annular wall 420 surrounding a compartment,such as a through opening 422, for receiving bone growth material. Theannular wall 420 includes an upper bone engaging portion 424 and a lowerbone engaging portion 426. The annular wall 420 extends from the upperto the lower bone engaging portion 424, 426 and around the throughopening 422 without interruption. By extending without interruption, itis intended to mean that there are no through apertures in communicationwith the through opening 422 that extend from the inner surface 430 tothe outer surface 438. This increases the strength of the annular wall420 by limiting stress concentrating features.

With reference to FIG. 15, the upper and lower bone engaging portions424, 426 include a plurality of gripping members 440 each having arounded peak 442 and rounded leading and trailing surfaces 444, 446. Thegripping members 440 thereby have an undulating shape along the upperand lower bone engagement portions 424, 426. The upper and lower boneengaging portions 424, 426 are tapered to have angles 450, 452 relativeto a longitudinal axis 454 of the body 202. This tapered profile of theimplant 200 aids in insertion of the implant 200 between vertebrae.

With reference to FIG. 16, the inner surface 430 of the annular wall 420extends around a central, vertical axis 450 of the body 402. The annularwall 420 includes nubs 432 and crisscrossing or intersecting pathways434. The nubs 432 and pathways 434 are similar to the nubs 16, 232 andpathways 54, 268 discussed above. The nubs 432 have varying sizes alongthe inner surface 430. For example, the nubs 432 include nubs 432A thatare truncated or reduced in size near an upper surface 452 of theannular wall 420. The nubs 432 include nubs 432B that are larger thannubs 432A but are partially truncated or reduced in size relative tonubs 432C. The nubs 432C are more toward the middle of the annular wall420 and not truncated and have a full diamond shape. The body 402 mayalso include one or more bores 456 that receive marker pins 458.

With reference FIG. 17, the dovetail projection 414 includes inclinedwalls 460, 462 and walls 464, 466 that extend transversely to theinclined walls 460, 462. The dovetail projection 414 provides a thickstructure to receive the compressive forces from the arms of an insertertool. Further, the walls 464, 464 may abut surfaces of the inserter toolto absorb impacts from the inserter tool such as impacts due to asurgeon striking the inserter tool with a mallet to urge the implant 400into an intervertebral space. As shown in FIG. 18, the body 402 includesceilings 470 and floors 472 that form upper and lower boundaries of therecesses 410, 412.

With reference to FIG. 19, the process of fabricating the body 402 ofthe implant 400 involves providing a model 504 to a computer thatcontrols operation of a selective laser sintering machine. The computeruses the model 504 to direct a laser of the machine to fuse particles ofa bed of PEKK into layers and forms a printed body 402A by progressivelyprinting one layer after another. The machine starts building the layersof the body 402 by first fusing particles of PEKK to form a skin downsurface 500. The machine progressively forms layers one below another indirection 501 until the machine reaches a skin up surface 502 of theprinted body 402A. Due to the sintering method used to melt theparticles in the PEKK bed, the process may have a lower resolution atthe skin down surface 500 then the skin up surface 502. Morespecifically, the laser hits the particles of the PEKK bed with the mostenergy when the laser begins to form a first layer, i.e., the skin downsurface 500 of the printed body 402A. More particles are added to bedabove the first layer, and the laser is directed to form a second layerabove the first layer. This process is repeated until the final layerincluding the skin up surface 502 has been formed. The laser has lessenergy when it is forming the second and higher layers such that thoselayers have more accuracy than the first layer.

To compensate for this, the model 504 provided to the computerassociated with the selective laser sintering machine may haveexaggerated geometry so that printed body 402A that results from theselective laser sintering has the desired geometry. For example, themodel 504 may have lower gripping members 506 that have a peak-to-valleyheight 508 that is greater than a peak-to-valley height 510 of thegripping members 440 of the body 402A that result from the selectivelaser sintering process. In other words, the gripping members 506 of themodel 504 provided to the selective laser sintering machine are moreexaggerated than the gripping members 440 that result from the 3Dprinting process. The difference in a height 508, 510 is due to thelower resolution at the skin down surface 502 causing the grippingmembers 440 to be smaller than the gripping members 506. Other featuresof an implant may be emphasized or reduced in the model 504 provided tothe selective laser sintering machine. For example, the curvature ofpeaks 512 of the gripping members 506 may be different than thecurvatures of the peaks 442 of the printed body 402A.

With reference to FIG. 20, the selective laser sintering machineproduces the printed body 402A. The printed body 402A includes thegripping members 440, the nubs 432, and the through opening 422. Theprinted body 402A is then machined 520 to impart structural details tothe printed body 402A that require higher precision than provided by theselective laser sintering process. For example, the recesses 412, 416and marker pin bores 456 are machined into the printed body 402A toproduce the body 402. The process of machining the recesses 412, 416into the 3D body 402 produces the smooth machined surfaces 416 of thebody 402.

With reference to FIG. 21, fabricating the body 15 includes producing aprinted body 15A by selective laser sintering PEKK. The printed body 15Aincludes the gripping members 62, nubs 14, 16, and through opening 35.The printed body 15A is machined 530 to form the nose 22, recesses 26,28, boss 140, trailing end surface 144, and marker pin apertures 120,122 into the printed body 15A. This produces the body 15 discussedabove. The machining 530 imparts the smooth machined surfaces 30, 32 ofthe body 15.

With reference to FIG. 22, fabricating the body 202 includes producing aprinted body 202A by selective laser sintering PEKK. The printed body202A includes the through opening 221, the web 226, the gripping members254, and the nubs 232. The printed body 202 is then machined 540 to formthe nose 210, recesses 214, 216, trailing end surface 284, and boss 290into the body 202A. The machining 540 imparts the smooth machinedsurfaces 212, 217.

With reference to FIGS. 23, 24, and 25, the implant bodies are shown intheir respective orientations during fabricating of the implant bodiesby selective laser sintering the particles of the PEKK bed. As shown inFIG. 23, the printed body 402A is positioned so that the skin up surface500 and the skin down surface 502 contain the gripping members 440.

With reference to FIG. 24, the orientation of the implant body duringthe selective laser sintering process may be selected to position loweraccuracy portions of the implant body at regions of the implant bodythat are machined off. For example, the printed body 15A may bepositioned to have the skin up surface 550 be at the trailing endportion 20 of the printed body 15A and a skin down surface 554 be at theleading end portion 18 of the body 15A. As discussed above, the printedbody 15A is machined 530 to form the nose 22, recesses 26, 28, boss 140,and trailing end surface 144. Because the printed body 15A is beingmachined to form these features at the leading and trailing end portions18, 20, inaccuracies at the skin up and skin down surfaces 550, 554 areremoved by the machining process.

With reference to FIG. 25, the printed body 202A may be positioned sothat the trailing end portion 206 of the printed body 202A is at a skinup surface 562 and the leading end portion 208 is at a skin down surface568. In this manner, any imperfections that occur at the skin up andskin down surfaces 562, 568 are machined off when the recesses 214, 216,boss 290, and nose 210 are machined into the printed body 202A.Additionally, orienting the body 202A so that it prints along a diagonalpath, rather than vertical or horizontal, reduces unintended curvatureof the body 202A that may result from the selective laser sinteringprocess.

With reference to FIG. 26, testing was performed to provide anunderstanding of the bone fusion properties provided by the implants 10,200, 400 discussed above. The testing included an in vivo ovine bonedefect study. The study was designed to evaluate biomechanical push-outstrength, bone apposition, and bone area of implants including titaniumcoated PEEK implants 600, uncoated PEEK implants 602, and implants 604manufactured by selective laser sintering PEKK material. The implants600 had a roughened outer surface of the titanium material. The implants604 included diamond-shaped nubs 606 and pathways 608 separating thenubs 606. Because the implants 604 were produced by selective lasersintering PEKK, the implants 604 had a rough exterior surface 610similar to the rough exterior surfaces of the implants 10, 200, and 400discussed above.

The implants 600, 602, 604 were cylinder shaped with an outer diameterof 6 mm and a total length of 30 mm. The implants 600, 602, 604 wererandomly placed into distal femurs of sheep and allowed to heal for aneight-week time period or a sixteen-week time period. Six implants ofeach type of implant 600, 602, 604 were implanted for each time period,with three samples per implant type per time period analyzed forpush-out testing and three for histological analysis. Histologicalanalysis included fibrosis and immune response assessment using scanningelectron microscopy and light microscopy methods. Biomechanical push-outtesting was also performed to assess a peak push-out force.

The imaging and histological analyses demonstrated new viable bonesurrounding the implants 600, 602, 604. Osteoblast activity suggestedthe bone to be viable and actively remodeling in the periprosthetic boneregion with all three implant types. Bone area in periprosthetic regionincreased from 26.7 to 40.1% with implant 604, from 14.9 to 35.4% withimplant 600, and 40.1 to 47.6% with implant 602. Bone organization andmaturation progressed between 8 and 16 week time points.

Periprosthetic regions had similar distribution of trabecular bone andmarrow space in all groups but the groups using implant 602 showedhigher degree of fibrotic membrane formation around the implants. Boneapposition increased from 3.6% to 34.1% of implant area with implants604, from 10.5 to 52.3% with implants 600, and decreased from 40% to 16%with implants 602 by 16 weeks. Excellent osseointegration was achievedwhen implants 604 and 600 were implanted in close approximation to thebone. The implants 602 showed more “spot welding” osseointegration withlimited mechanical interlock. No adverse reaction was observed to anyimplant type.

The histological analysis showed that the topography of the implants604, which included the nubs 606 and rough exterior surface 610resulting from selective laser sintering PEKK to fabricate the implants604, provided larger area for progressive bone growth beyond the eightweek time point differently from the implants 600, 602. Bony ingrowth onthe implants 604 followed surface topography and filled the micro poresof the implants 604 demonstrating excellent osteoconductivecharacteristics of the implants 604.

Push-out strength significantly increased with the implants 604 and 600by eight weeks, which is indicative of early and rapid osseointegration.The overall peak force in the group of implants 604 (2819.9 N) was overten fold higher than the group of implants 602 (230.0N) and about 40%lower than group of implants 600 (4682.9N) by the sixteen-week endpoint. The results of the pushout testing are provided in a graph 640 ofFIG. 30.

FIG. 27 contains pictures of implants 600, 602, 604 removed duringpush-out testing at the sixteen week end point. The abundance ofcancellous bone attached to the pushed-out implants 604 supportedhistological observations of significant osseointegration of implants604 and suggested that the bond between implant and host bone wasstronger than the breaking point of native cancellous bone.

On the other hand, the implants 600 had minimal amount of attached bone.The implants 602 had no bone attached.

With reference to FIGS. 28A-C and 29A-C, the study included performinglight microscopy after the sixteen week end point for the implants 600,602, 604. The images of FIGS. 28A-C and 29A-C are cross-sectional viewsof implants 600, 602, 604 showing bone apposition and ingrowth. Theimages of FIGS. 29A-29C show marrow spaces 613 and bone 614 around theimplants 600, 602, 604. The implant 600 had apposition of bone withminimal fibro-connective tissue ingrowth. The implant 602 had largeareas of fibro-connective membrane 611 between the bone and the implant602 and only regional areas 612 of the bone 614 stitching to the implant602. The implant 604 had bone ingrowth into the surface structure of theimplant 604 that filled the topography of the implant 604 with good boneapposition. The bone ingrowth into the topography of the implant 604included bone 614 surrounding and engaging with the nubs 606 as well asthe bone 614 filling in and engaging pores 618 of the rough exteriorsurface 610 of the implant 604.

In sum, the implants 604 demonstrated superior osteoconductiveproperties over the implants 602 with excellent osseointegration intocancellous bone of distal femur similar to implants 600. There was no orminimal fibrosis next to implants 604 and 600 when compared to implants604. The typography of the implants 604, including the nubs 602 and therough exterior surface 610, endorsed superior bone ingrowth andintegration into cancellous bone which occurred by new bone ingrowthinstead of apposition as with the implants 600, 602. The peak push outforce significantly increased overtime with implants 604, 600 but notwith implants 602. The implants 604 did not show interference withroutine imaging methods (such as x-rays) used in clinic, unlike theimplant 600 which would be radiopaque due to the titanium coating.

It has also been discovered that an implant fabricated by selectivelaser sintering PEKK has better antibacterial properties in comparisonto a conventional PEEK implant. In particular, bacteria and biofilmformation were studied for these two types of implants. Bacteria celllines used in this study were S. epidermidis and P. aeruginosa.Fluorescence confocal microscopy was used to visualize the colonizationof bacteria on the samples of interest. The results of this studyrevealed that both of these two bacteria adhered and grew less on thenano-featured PEKK material substrates as compared to the PEEK material.In particular, the Gram-negative bacteria (P. aeruginosa) attached andgrew less on the PEKK implant when compared to the Gram-positivebacteria (S. epidermidis) on the PEEK implant. More specifically, thePEKK implant had more than a 55% anti-bacterial effect for P. aeruginosaand a 40% anti-bacterial effect for S. epidermidis as compared to thePEEK implant. It is believed that the nano-rough surface of the PEKKimplant changes surface energy which in turn can enhance select proteinabsorption important for inhibiting bacteria attachment and growth.

With reference to FIG. 31, an inserter tool 700 is provided foradvancing the implant 10 through a surgical passageway and into positionbetween vertebrae. The inserter tool 700 includes a distal end portion702 for selectively engaging the implant 10 and a proximal end portion704 having a handle 706. The inserter tool 700 includes a shaft assembly705 that supports a pivotal clamping arm 708 and a fixed arm 710. Theinserter 710 includes an actuator, such as an adjustment knob 712, whichmay be shifted in direction 714 toward the handle 706 to an openposition to pivot the clamping arm 708 to a release position. Thisallows a user to position the attachment member 24 of the implant 10between the arms 708, 710. The user then shifts the adjustment knob 712in direction 716 away from the handle 706 to a closed position to pivotthe clamping arm 708 to a clamping position and clamp the attachmentmember 24 between the arms 708, 710. The inserter tool 700 includes alock knob 720 having a body 739 that a user may turn in direction 722 tolock the adjustment knob 712 in the closed position. This provides apositive mechanical lock to resist movement of the arm 708 away from thearm 710 and maintain the connection between the distal end portion 702and the implant 10.

With reference to FIG. 32, the shaft assembly 705 includes an outersleeve 730 and an inner shaft 732 within the sleeve 730 that is moveablein directions 714, 716 to pivot the clamping arm 708. The inserter tool700 includes a rear shaft 734 releasably secured to the outer sleeve730. The lock knob body 739 has internal threads 736 that engageexternal threads 738 of the rear shaft 734. The lock knob 720 includes aknob cap 740 connected to the body 739.

The adjustment knob 712 includes a pin 742 that extends through anaxially elongated opening of the rear shaft 734 and through anon-axially elongated opening 746 of the inner shaft 732. Thus, when theadjustment knob 712 is shifted in direction 714, the pin 742 transfersthe movement of the adjustment knob 712 into movement of the inner shaft732 in direction 714. The elongated opening of the rear shaft 734permits the pin 742 to travel within a predetermined range of motionwithin the rear shaft 734.

The lock nob 720 houses a ring 743 extending around a distal end portion745 of the adjustment knob 712. The pin 742 has ends that are receivedin non-axially elongated openings of the ring 743. The pin 742 therebyjoins the ring 743, adjustment knob 712, and inner shaft 732 so that thering 743, adjustment knob 712, and inner shaft 732 shift together indirections 714, 716.

Shifting the knob 712 and inner shaft 732 in direction 714 furthercompresses a spring 750 received in a cavity 752 of the rear shaft 734.The spring 750 may be partially compressed when the adjustment knob 712and inner shaft 732 are in the closed position such that the surgeonmust further compress the spring 750 in order to shift the adjustmentknob 712 and inner shaft 732 to the open positions thereof. The surgeonholds the adjustment knob 712 in the open position to keep the arm 708pivoted to its release position.

In one form, the clamping arm 708 is part of an ejecting clamp 780 (seeFIG. 33). Once the surgeon positions the implant attachment member 24between the arms 708, 710, the surgeon releases the adjustment knob 712.The spring 750 urges the inner shaft 732 and adjustment 712 distally indirection 716 which pivots the ejecting clamp 780 in direction 798 andcauses the arms 708, 710 to clamp the implant attachment member 24therebetween.

To lock the ejecting clamp 780 and arm 708 thereof in the clampingposition, the surgeon turns the lock knob 720 in direction 722 whichcauses the lock knob 720 to shift distally in direction 716. The lockingknob cap 740 has a flange 747 that abuts the ring 743 and urges the ring743/pin 742 assembly in direction 716. The surgeon tightens the lockingknob 720 in direction 722 so that the engagement between the threads736, 738 of the lock knob 720 and outer shaft 734 keeps the flange 747urging the pin 742 in direction 716. In this manner, tightening the lockknob 720 in direction 722 causes the lock knob flange 740 to inhibit thepin 742, inner shaft 732, and adjustment knob 712 from shifting indirection 714 and permitting the arm 708 to pivot to its releaseposition. This locks the arm 708 in the clamping position thereof untilthe surgeon turns the lock knob 720 in direction 723 to shift the lockknob flange 740 in direction 714, which spaces the flange 747 axially upthe rear shaft 734 from the pin 742 and provides space for the pin 742to shift in direction 714.

With reference to FIG. 32, the handle 706 includes a handle outerportion 770, a handle inner portion 772, and a handle adaptor bolt 774that connects the handle outer and inner portions 770, 772 to the rearshaft 734. The handle 706 includes a handle lock nut 776 and a spacer778 for securing the handle inner portion 772 to the rear shaft 734.

With reference to FIG. 33, in one form, the ejecting clamp 780 has aprotrusion 782. When the ejecting clamp 780 is pivoted in direction 799,the protrusion 782 contacts the head portion 132 of the implantattachment member 24 and pushes the implant attachment member 24 outfrom between the arms 708, 710 which assists the surgeon indisconnecting the inserter tool 700 from the implant 10.

The outer sleeve 730 includes a clamp housing 784 and the fixed arm 710is integrally formed with the clamp housing 784 as shown in FIG. 33. Theinserter distal end portion 702 includes a pin 786 that pivotallyconnects the ejecting clamp 780 to the clamp housing 784. The inserterdistal end portion 702 further includes a pin 788 connecting theejecting clamp 780 to an end portion 790 of the inner shaft 732. Theinner shaft 732 includes a flexible portion 792 that may have a reducedcross-sectional thickness as compared to a proximal portion 794 of theinner shaft 732. The flexible portion 792 may bend to compensate forpivoting of the ejecting clamp 780 in direction 799 when the inner shaft732 is shifted proximally in direction 714. Conversely, the inner shaft732 shifting in distally direction 716 causes the ejecting clamp 780 topivot in direction 798. The components of the inserter tool 700including the shaft 732, sleeve 730, arm 710, clamp 780 may be made ofstainless steel such as 17-4 or 465 stainless steel.

With reference to FIG. 34, the arms 708, 710 and implant 10 have matingportions configured to fix the implant 10 to the arms 708, 710 with thearms 710 clamping the attachment member 24 therebetween. The matingportions provide a positive mechanical interlock between the insertertool 700 and the implant 10 that ensures the implant 10 is correctly andfirmly grasped by the inserter tool 700. For example, the arms 708, 710may have protrusions 735 configured to fit into recesses 737 formed bythe neck 130 and head 132 of the attachment member 24. The arms 708, 710have surfaces 739 that conform to surfaces 741 of the neck 130 and head132 of the attachment member 24. In this manner, the implant 10 islocked to the inserter distal end portion 702 and generally cannot twistor slide relative to the distal end portion 702.

The attachment member 24 includes tapered surfaces 804 on opposite sidesof the head portion 132 of the attachment member 24 and the protrusions735 of the arms 708, 710 include tapered surfaces 806 that engage thesurfaces 804. The surfaces 804, 806 are inclined relative to thelongitudinal axis 113 of the implant 10.

In FIG. 34, the inner shaft 732 has been shifted distally in direction716 to pivot the ejecting clamp 780 to the clamping position thereof.The clamping arm 708 of the ejecting clamp 780 compresses the implantattachment member 24 against the arm 710. This compression urges thesurface 804 of the head portion 132 of the attachment member 24 againstthe surfaces 806 of the arms 708, 710. The surfaces 804, 806 extendtransversely to the longitudinal axis 113 of the implant 10. Theengagement of the surfaces 804, 806 urges the attachment member 24 inproximal direction 714 and presses the implant trailing end surface 144against upper and lower portions 820, 822 (see FIG. 35) of the clamphousing 784. In this manner, the material of the attachment member 24 iscompressed generally between the protrusions 735 of the arms 708, 710and the clamp housing upper and lower portions 820, 822.

The engaged surfaces 804, 806 of the implant attachment member 24 andthe arms 708, 710 also direct compression of the attachment member 24due to manipulation of the inserter tool 700 along diagonal pathsoblique to the longitudinal axis 26 of the body 15. More specifically,manipulating the inserter tool 700 in lateral direction 821 when theimplant 10 has been advanced partially between vertebrae causescompression of the attachment member 24 generally along a transversepath 809. The compression is due at least in part on the arm 710 pushingdistally on the attachment member 24 and the arm 708 pulling proximallyon the attachment member 24. The transverse path 809 extends from theprotrusion 735 of the arm 708 to the trailing end surface 144 of theattachment member. Similarly, manipulating the inserter tool 700 inlateral direction 823 causes compression of the attachment member 24 toact generally along a transverse path 810 between the protrusion 735 ofthe arm 710 and the trailing end surface 144. If the clamping arms 708,710 only applied compression in a lateral path across the attachmentmember 24 when the inserter tool 700 was manipulated in directions 821,823, such compression would act through a distance 812 of the attachmentmember 24. As shown in FIG. 34, the distance 816 along transverse path810 is greater than the distance 812. This means that a greaterthickness of material of the attachment member 24 is subjected to thecompressive forces due to the engagement between surfaces 804, 806 whenthe inserter tool is manipulated in directions 821, 823. By increasingthe material of the attachment member 24 subject to the compressionforces, the attachment member 24 may be strengthened to resist loadingduring manipulation of the inserter tool 700.

With reference to FIG. 35, the upper and lower portions 820, 822 of theclamp housing 784 define a socket 824 for receiving the boss 140 of theimplant 10. This creates confronting surfaces 826, 828 and 830, 832 thatcan transfer loading from the inserter tool 700 to the implant 10. Morespecifically, if the upper and lower bone engaging portions 55, 56 arepositioned partway into a space between vertebrae, and the surgeon liftsup the handle 706 in direction 840, the surfaces 826, 828 and 830, 832can abut and transfer the loading from the inserter tool shaft 705 tothe implant 10. The boss 140 thereby increases the axial length ofengagement between the implant 10 and the inserter tool 700 along thelongitudinal axis 113 of the implant 10. The loading from the lifting ofthe shaft 705 in direction 840 is also transferred to the implant 10 byway of the arms 708, 710 pressing against the ceilings 850 and floors852 (see FIG. 6) of the body 15.

With reference to FIGS. 36, 37, and 38, a method of connecting theimplant 10 to the inserter tool 700 is provided. Initially, the lockknob 720 is in an unlocked position and the adjustment knob 712 has beenshifted in direction 714 to the proximal, open position as shown in FIG.36. This causes the clamp arm 708 to pivot to the release position. Theimplant 10 may be then be advanced in direction 714 to position theattachment member 24 between the arms 708, 710. Next, the adjustmentknob 712 is released and the spring 750 urges the inner shaft 732 andadjustment knob 712 distally in direction 716 as shown in FIG. 37. Theshifting of the inner shaft 732 in direction 716 causes the arm 708 topivot in direction 798 and clamp the attachment member 24 between thearms 708, 710. As shown in FIG. 37, the arms 708, 710 are within theenvelope of the implant 10 and do not extend laterally outward from theimplant 10 which makes the implant 10 easier to advance into thepatient.

Next, the lock knob 720 is turned in locking direction 722 as shown inFIG. 38.

This shifts the locking knob 720 in direction 716, brings the lockingknob flange 720 into contact with the ring 747, and inhibits the pin 742and inner shaft 732 connected to the ring 747 from shifting in direction714. This locks the clamping arm 708 in the clamping position and keepsthe arms 708, 710 clamping the implant attachment member 24therebetween.

With reference to FIG. 39, an inserter 900 is provided for positioningthe implant 200 between vertebrae. The inserter 900 includes a handleassembly 902 and a shaft assembly 904 that is releasably connected tothe handle assembly 902 by a quick release mechanism 906 of the handleassembly 902. The shaft assembly 904 includes a proximal end portion 910having a control knob 912 and a distal end portion 914 having arms 916,918.

With reference to FIG. 40, the handle assembly 902 has a socket 920 thatreceives a drive member 922 of the shaft assembly 904. The quick releasemechanism 906 includes a spring and a sleeve 930 that is urged by thespring in direction 932 to a retention position. When the sleeve 930 isin the retention position, the sleeve 930 shifts detent balls of thequick release mechanism 906 radially inward such that the detent ballsresist removal of the drive member 922. To release the shaft assembly904 from the handle assembly 902, the sleeve 930 is shifted in direction934 against the bias of the spring which permits the detent balls toshift radially outward and allows the drive member 922 to be withdrawnfrom the socket 920.

The shaft assembly 904 includes an outer sleeve 940 and an inner shaft942. The inner shaft 942 is threadedly engaged with the knob 912. Theinner shaft 942 is connected to an inserter fork 944 having resilientfork members 946, 948 that are separated from each other by a gap 950.The fork members 946, 948 include the arms 916, 918. To shift the arms916, 918 toward one another, the knob 912 is turned in direction 952which draws the inserter shaft 952 proximally in direction 934. Theproximal shifting of the inserter shaft 942 in direction 934 causescamming engagement between surfaces 960, 962 of the outer sleeve 940 andfork members 946, 948. This camming engagement shifts the arms 916, 918toward each other. To release the inserter arms 916, 918 from theimplant 200, the knob 912 is turned in a direction opposite direction952 to shift the inner shaft 942 and inserter fork 944 distally and theresilient properties of the fork members 946, 948 urge the arms 916, 918apart.

With reference to FIG. 41, the inserter tool 900 engages the implant 200in a manner similar to engagement between the inserter tool 700 and theimplant 10. The arms 916, 918 have projections 963 that extend into thecavities 300, 302 and mate with walls 961 of the attachment member 215.The arms 916, 918 also include tips 962 that extend along walls 964 ofthe implant 200. The arms 916, 918 also include inner surfaces 966 thatpress against and engage surfaces 968 of the attachment member 215.

With reference to FIG. 42, one difference between the inserter tools700, 900 is that the inserter 900 has a socket 980 defined by the arms916, 918 rather than the outer sleeve 940. The socket 980 engages theboss 290 of the implant 200 to improve the strength of the connectionbetween the implant 200 and the inserter 900. The socket 980 includessurfaces 982, 988 that contact surfaces 984, 986 of the boss 290 andincrease the longitudinal extent of the engagement between the implant200 and the inserter 900. The arms 916, 918 also engage the ceilings 990and floors 992 (see FIG. 12) of the body 202 to transfer loading such asby lifting of the shaft assembly 904 in direction 996 to the implant200.

With reference to FIG. 43, an inserter tool 1100 is provided forpositioning the implant 400. The inserter tool 1100 is similar in manyrespects to the inserter tools 700, 900 discussed above such thatdifferences between the inserters will be discussed. The inserter tool1100 has a proximal end portion 1102 with a rotatable handle 1104 and adistal end portion 1106 with arms 1108, 1110 for releasably clamping theimplant 400. The inserter tool 1100 includes a shaft assembly 1112having an outer shaft 1114 and an inner shaft 1116. Turning the handle1104 in direction 1118 draws the inner shaft 1116 proximally indirection 1120. The inner shaft 1116 includes resilient fork members1122, 1124 that include the arms 1108, 1110. The shifting of the innershaft 1116 proximally in direction 1120 causes camming engagementbetween surfaces 1130 of the arms 1108, 110 and a surface 1132 of adistal end portion 1134 of the outer shaft 1114. This urges the arms1108, 1110 together in directions 1140, 1142 to clamp the dovetailprojection 414 of the implant 400 therebetween. Conversely, turning thehandle 1104 in a direction opposite to direction 1118 shifts the innershaft 1116 distally in direction 1144 and the resiliency of the forkmembers 1122, 1124 causes the arms 1108, 1110 to shift apart.

The arms 1110, 1112 include projections 1150 that are positioned in therecesses 410, 412 on opposite sides of the dovetail projection 414. Withreference to FIG. 45, turning of the handle 1104 in direction 1118 hasurged the inner shaft 1116 proximally in direction 1120 and has engagedthe arms 1108, 1110 against the dovetail projection 414. The arms 1108,1110 are shaped to form a dovetail recess 1160 between the arms 1108,1110 that has a mating fit with the dovetail projection 414. Further,the projections 1150 have inclined surfaces 1162 that engage inclinedsurfaces 1164 of the dovetail projection 414 and urge the implant 400tightly into engagement with the arms 1108, 1110 as the arms 1108, 1110clamp the dovetail projection 414 therebetween.

The arms 1108, 1110 include flats 1170 that abut the walls 464, 466 ofthe implant 400. During insertion of the implant 400, the surgeon maytap a hammer on a proximal end 1180 of the handle 1104 and the inserter1100 transmits these impacts against the implant 400 by way of theengagement between the flats 1170 and the walls 464, 466.

While there have been illustrated and described particular embodimentsof the present invention, it will be appreciated that numerous changesand modifications will occur to those skilled in the art, and it isintended for the present invention to cover all those changes andmodifications which fall within the scope of the appended claims.

What is claimed is:
 1. A spinal implant for fusing vertebral bones, thespinal implant comprising: a monolithic body for being inserted betweenbones; a through opening of the body for receiving bone growth material;a wall of the body extending about the through opening; and nubs of thewall extending into the through opening for increasing surface area ofthe wall available for bone on-growth.
 2. The spinal implant of claim 1wherein the wall includes a plurality of intersecting pathways for thebone growth material that separate the nubs.
 3. The spinal implant ofclaim 1 wherein the wall includes an upper bone engaging portion and alower bone engaging portion and the wall includes pathways extendingfrom the upper bone engaging portion to the lower bone engaging portion.4. The spinal implant of claim 1 wherein the wall includes a basesurface separating the nubs and each nub has a continuous side surfaceprojecting from the base surface and defining an outer periphery of thenub spaced from the continuous side surface of adjacent nubs.
 5. Thespinal implant of claim 4 wherein the continuous side wall of each nubincludes at least three side wall surface portions connected by edges ofthe nub.
 6. The spinal implant of claim 1 wherein the body is ofpolyetherketoneketone (PEKK) and the body is fabricated using selectivelaser sintering.
 7. The spinal implant of claim 1 wherein the nubs eachhave a diamond shape.
 8. The spinal implant of claim 1 wherein the wallincludes an inner surface that includes the nubs and an outer surfaceopposite the inner surface and the outer surface includes a plurality ofsecondary nubs.
 9. The spinal implant of claim 8 wherein the nubs andthe secondary nubs each have a diamond shape.
 10. The spinal implant ofclaim 1 wherein the wall of the body includes wall portions extendingalong opposite sides of the through opening, the wall portions eachhaving an upper bone-engaging portion and a lower bone-engaging portion;a web of the body interconnecting the wall portions and extending acrossthe through opening; uppermost and lowermost portions of the web thatare recessed relative to the corresponding upper and lower bone-engagingsurfaces of the wall to avoid contact between the web and the bonesduring insertion of the implant into a space between the vertebralbones.
 11. The spinal implant of claim 10 wherein the wall portions eachinclude nubs above and below the web.
 12. An implant for being insertedinto an intervertebral space between vertebrae to stabilize thevertebrae, the implant comprising: a monolithic body ofpolyetherketoneketone (PEKK), the body being fabricated using selectivelaser sintering; a through opening of the body for receiving bone growthmaterial; an annular wall of the body extending about the throughopening and having upper and lower bone engaging portions; the annularwall being free of through apertures in communication with the throughopening; an attachment member of the body outward of the annular wall;and recesses of the body extending along opposite sides of theattachment member configured to receive clamping arms of an insertertool.
 13. The implant of claim 12 wherein the body has a leading endportion and a trailing end portion and a longitudinal axis extendingtherebetween and the attachment member includes a boss that increasesthe axial length of the attachment member for being engaged by theinserter tool.
 14. The implant of claim 12 wherein the attachment memberincludes ramp surfaces at opposite sides of the attachment member thatdefine at least a portion of the recesses and extend transverse to eachother, the ramp surfaces configured so that the body shifts toward theinserter tool as the clamping arms clamp the attachment member.
 15. Theimplant of claim 12 wherein the attachment member includes lateralcavities at the opposite sides of the attachment member that receiveprojections of the inserter instrument clamping arms.
 16. The implant ofclaim 12 wherein the attachment member is unthreaded.
 17. The implant ofclaim 12 wherein the annular wall has an inner surface extending alongthe throughbore and an outer surface opposite the inner surface, and theannular wall has a minimum thickness between the inner and outersurfaces thereof of at least approximately 0.06 inches throughout theentire wall.
 18. The implant of claim 12 wherein the body includes poreshaving an average diameter in the range of approximately 500 toapproximately 600 micrometers to encourage bone cell on-growth.
 19. Theimplant of claim 12 wherein the inner surface of the annular wallincludes nubs projecting into the through opening.
 20. The implant ofclaim 19 wherein the annular wall includes a plurality of intersectingpathways separating the nubs.
 21. The implant of claim 12 wherein thebody includes openings and marker pins received in the openings, and themarker pins each have a plurality of edges spaced from each other aboutthe marker pin that engage the body and retain the marker pin in thebody opening.
 22. The implant of claim 12 wherein the body includes aleading end portion and a trailing end portion, the trailing end portionincluding the attachment member.
 23. A spinal implant comprising: apolymer body fabricated using additive manufacturing; unmachined,irregular surfaces of the body; and a machined attachment portion of thebody configured to interface with an inserter tool, the machinedattachment portion having a surface roughness that is less rough than asurface roughness of the unmachined, irregular surfaces of the body. 24.The spinal implant of claim 23 wherein the machined attachment portionof the body includes an attachment member and recesses at opposite sidesof the attachment member.
 25. The spinal implant of claim 23 wherein thebody includes a leading end portion and a trailing end portion and alongitudinal axis extending therebetween, and the machined attachmentportion includes an axially extending boss.
 26. The spinal implant ofclaim 23 wherein the body includes a through opening for receiving bonegrowth material and nubs extending into the through opening and theunmachined, irregular surfaces of the body include surfaces of the nubs.27. The spinal implant of claim 23 wherein the body includes a machinednose portion having a surface roughness that is less rough than thesurface roughness of the unmachined body surfaces.
 28. The spinalimplant of claim 23 wherein the body is made of polyetherketoneketone(PEKK) and is fabricated using selective laser sintering.
 29. The spinalimplant of claim 23 wherein the body includes a through opening forreceiving bone growth material and an annular wall extending about thethrough opening, the annular wall including nubs extending into thethrough opening for increasing the surface area of the wall availablefor bone on-growth.
 30. The spinal implant of claim 23 wherein the bodyincludes a through opening for receiving bone growth material and anannular wall extending about the through opening, the annular wallhaving upper and lower bone engaging portions and being free of throughapertures in communication with the through opening.
 31. The spinalimplant of claim 23 wherein the surface roughness of the unmachined,irregular surfaces of the body is in the range of 30-60 roughnessaverage and the surface roughness of the machined attachment portion isin the range of 900-1100 roughness average.
 32. The spinal implant ofclaim 23 wherein the body includes a through opening for receiving bonegrowth material and an annular wall extending about the through opening;wall portions of the annular wall extending along opposite sides of thethrough opening, each wall portion including an upper bone engagingportion and a lower bone engaging portion; a web of the bodyinterconnecting the wall portions and extending across the throughopening; and uppermost and lowermost portions of the web that arerecessed relative to the corresponding upper and lower bone-engagingsurfaces of the wall to avoid contact between the web and vertebralbones during insertion of the implant into a space between the vertebralbones.
 33. A spinal implant system comprising: a spinal implant having aleading end portion, a trailing end portion, and a longitudinal axisextending therebetween; an attachment member of the trailing endportion; a trailing end surface of the attachment member; a boss of theattachment member extending axially outward from the trailing endsurface; and an inserter tool comprising: arms having a releaseconfiguration that permits the arms to be positioned on opposite sidesof the attachment member and a gripping configuration wherein the armsclamp the attachment member therebetween; and a socket configured toengage the boss of the attachment member and increase the axial lengthof the engagement between the inserter tool and the implant.
 34. Thespinal implant system of claim 33 wherein the arms include the socket ofthe inserter tool.
 35. The spinal implant system of claim 33 wherein theinserter tool includes a shaft assembly having a sleeve and the sleeveincludes the socket.
 36. The spinal implant system of claim 33 whereinthe implant includes recesses on opposite sides of the attachment memberthat receive the arms.
 37. The spinal implant system of claim 33 whereinthe spinal implant includes a body of polyetherketoneketone (PEKK), thebody being fabricated using selective laser sintering;
 38. The spinalimplant system of claim 33 wherein the inserter tool includes an outersleeve and an inner shaft connected to the arms and shiftable relativeto the outer sleeve, the outer sleeve and inner shaft including surfacesconfigured to shift the arms between the release and grippingconfigurations with shifting of the inner shaft and outer sleeverelative to each other.
 39. A method of producing a spinal implant, themethod comprising: fabricating a body of the spinal implant made of apolymer material using an additive manufacturing process, the bodyincluding irregular outer surfaces having a first surface roughnessproduced by the additive manufacturing process; and machining thefabricated body to form an attachment portion of the body forinterfacing with an inserter tool, the attachment portion having asecond surface roughness that is less rough than the first surfaceroughness of the irregular outer surfaces of the body.
 40. The method ofclaim 39 wherein fabricating the plastic body spinal implant using theadditive manufacturing process includes fabricating the body byselective laser sintering polyetherketoneketone (PEKK).
 41. The methodof claim 39 wherein fabricating the body using the additivemanufacturing process includes forming a skin-down surface and a skin-upsurface of the fabricated body; and machining the fabricated bodyincludes machining to remove the skin-down and skin-up surfaces from thefabricated body.
 42. The method of claim 39 wherein machining thefabricated body includes machining to form a nose portion of thefabricated body of the implant.
 43. The method of claim 39 whereinmachining the fabricated body includes machining at least one openinginto the body for receiving at least one marker pin.
 44. The method ofclaim 39 wherein fabricating the body of the spinal implant using theadditive manufacturing process includes providing a spinal implant modelto an additive manufacturing machine and using the additivemanufacturing machine to fabricate the body, the spinal implant modelincluding at least one portion having an exaggerated geometry tocompensate for changes in geometry that occur during fabrication of thebody.
 45. The method of claim 39 wherein the body has a longitudinalaxis and fabricating the body using the additive manufacturing processincludes adding layers of polymer material in a direction transverse tothe longitudinal axis.
 46. A marker pin for a spinal implant, the markerpin comprising: a body of a radiopaque material; a leading end portionof the body sized to fit into an opening of a body of a spinal implant;and an interference portion of the body radially enlarged relative tothe leading end portion and configured to engage the spinal implant bodyat a plurality of circumferentially spaced locations about the openingand retain the marker pin in the opening of the spinal implant body. 47.The marker pin of claim 46 wherein the interference portion includes aplurality of protrusions spaced about the body.
 48. The marker pin ofclaim 46 wherein the body includes a trailing end portion and alongitudinal axis extending between the leading and trailing endportions; and the interference portion includes a plurality oflongitudinally extending edges.
 49. The marker pin of claim 46 whereinthe interference portion includes a plurality of flat surfaces and edgesconnecting the flat surfaces.
 50. The marker pin of claim 46 wherein theinterference portion includes a plurality of flats and flat edgeportions connecting the flats.
 51. The marker pin of claim 46 whereinthe leading end portion has a circular cross-section, the body includesa trailing end portion having a circular cross-section, and theinterference portion has a non-circular cross section.